Method of forming pistons



Dec. 8, 1931. L w GREVE METHOD OF FORMING PISTONS Filed Aug. 6, 1928 illllllllll INVENTOR ril /la!!! Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE LOUIS W. GREVE, OF CLEVELAND, OHIO, ASSIGNOR TO THE CHAMPION MACHINE & FORGING COMIPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO METHOD OF FORMING PISTONS Application filed August 0, 1928. Serial No. 297,884.

This invention relates to a method of form-' ing pistons and like cup-shaped articles, and is intended particularly for the manufacture of aluminum or aluminum alloy pistons, although it is of fairly general application to the manufacture of cup-shaped articles of various kinds without particular regard to the metal or alloy employed.

So far as I am aware, forging has not been utilized heretofore in the manufacture of pistons because of the difficulty, if not impossibility, of withdrawing the male die from the forging. Internal projections of some kind, such as bosses or ribs, are necessarily used in order to provide bearings for the piston pin, and the formation of these projections has rendered it impossible heretofore to strip the forging from the die. Hence pistons have been made almost without exception of castings. Cast metal does not have a high strength-weight ratio because it is not compact. In other words, it is coarse in texture and. porous, as compared with the metal of forgings, and consequently cast metal parts must be made thicker and heavier than forged metal parts in order to render the same service.

In manufacturing pistons or other similar cup-shaped articles in accordance with my invention, I first produce a forging with walls which are inclined or tapered inwardly from the open end, the wall thickness being substantially as it should be in the finished article, and the necessary ribs, bosses or other projections being included in the wall formation in such a way that they do not interfere with the withdrawal of the male die. The resulting forging, the side wall of which is more or less conical in shape, is then subjected to a forming operation in which the side wall is brought up to a substantially cylindrical shape preferably by passing the article through a forming die of the proper diameter.

One of the objects of the present invention,

therefore, is to provide a method for produc-- ing pistons and other cup-shaped articles of forged metal, wherein any necessary internal bosses, ribs or other projections may be integrally formed and the desired wall thicknes imparted.-

Additional objects and advantages will become apparent hereinafter.

An embodiment of the apparatus which may be used in carrying out the invention is illustrated in the accompanying drawings wherein:

Figure 1 is a sectional view through a pair of die members showing a forging in position therebetween Fig. 2 is a sectional view throu h another pair of die members showing anot er step in the formation of the piston;

Fig. 3 is a vertical transverse section through the completed piston; and

Fig. 4 is a vertical section through the pistBon taaken at right angles to the section of 11 carrying out the invention, as applied to the manufacture of pistons, a heated blank of proper shape and containing the requisite amount of metal is subjected to a forging;

operation, being positioned in a suitable die composed of a die member 11 having a cupshaped die impression formed therein of a substantially inverted frusto-conical configuration and another die member 12 having a projection complementary to the recess in the die member 11, such projection being provided with diametrically opposed recesses adapted to form the internal bosses 10 or other suitably shaped internal projections for the piston pin. These die members 11 and 12 are relatively movable and are adapted when the blank is placed therebetween to form the same with a bottom portion 13 and an outwardly divergent wall portion 14, in other words, the blank is formed into substantially the same configuration as that of the die impression in the die member 11, the metal flowing into the recesses of, the projection of-the die member 12 to form the bosses 10.

The partly finished blank is then subjectedto a forming operation for the purpose of drawing the tapered walls up into cylindrical shape. For this purpose I prefer to employ two relatively movable die members, the outer one 9 of which is provided with a bore 15 of a diameter corresponding to the over-all diameter of the completed piston, the upper end of this bore 15 being formed with an outward flare 15a, such as the curved flare shown. The blank is positioned upon this die member 9 so that the bottom portion 13 thereof rests within the upper end of the bore 15, the divergent walls 14 resting attheir lower ends upon the outwardly curved flare portion 15a.

The other die element is indicated at 16 and comprises a cylindrical stem or projection of a diameter corresponding to the internal diameter of the completed piston, which stem may be carried by a suitable supporting member 17. The stem 16 is provided with a pair of diametrically opposed and suitably shaped recesses or depressions 18 adapted to receive the internal boss 10 of the piston when the piston has been finally formed into its completed shape. The two die members are now moved relative to each other whereupon the stem 16 passes into the bore 15, the bottom of the stem engaging the head 13 of the piston so as to force the same into the bore while the divergent side wall'la of the piston is turned up until it is substantially at right angles to the head, this movement of the side wall being permitted by the reception of the bosses 10 within the recesses 18 of the stem 16.

The piston has now been completely formed with a wall ofproper thickness and inwardly extending internal bosses 10 for the piston pins provided. The bosses 10 may now be drilled to provide bearings for the piston pin, and the necessary machining operations performed. Since the piston has been made by forging, the metal forming the .same is non-porous and hard and consequently may be designed with relatively thin walls, which means a saving in the weight of these rapidly reciprocating parts and an improvement in the efliciency and smoothness of operation of engines in which they may be employed.

Although a preferred embodiment of the invention has been illustrated and described herein it should be understood that the same is not limited thereto but is susceptible of such modifications and adaptations as fall within the scope of the appended claims, and that although the method has been described herein as particularly adapted to the formation of aluminum or aluminum alloy pistons it may be used in the formation of pistons of various kinds of metals or metal alloys and other cup-shaped articles of various kinds. Having thus described my invention, what I claim is: w

1. A method of forming cup-shaped articles, which comprises forginga blank into a substantially frusto-conical cup shape and providing during such operation an inwardly extending projection on the wall thereof, and then forming the blank so treated to reduce the side wall of the frusto-conical cup to substantially cylindrical form.

2. A method of forming pistons or the like, which comprises forging a blank into a sub stantially frusto-conical cup shape, the side wall and bottom of which are substantially of the proper thickness for the completed piston, and providing during such operation inwardly extending diametrically opposed projections on the wall thereof, and then forming the blank so treated to reduce the frustoconical wall thereof to substantially cylindrical form.

3. A method of producing a cup-shaped article having an internal projection upon the side wall thereof,-which comprises forging a blank with a head, a frusto-conical side wall and a projection on said side wall so shaped as to permit the withdrawal of the male die member when the forging operation is completed, and then drawing the thus partially formed blank through a cylindrical die to reduce the frusto-conical side wall to substantially cylindrical shape.

In testimony whereof, I hereunto affix my signature.

LOUIS \V. GREVE. 

